Method for controllably synthesizing cerium dioxide coated silica-based composite microspheres

Abstract

The invention discloses a method for controllably synthesizing cerium dioxide coated silica-based composite microspheres. The method comprises the following steps: dissolving a surfactant in ultrapure water to form a first solution, and dropwise adding a NaOH solution; heating the first solution, dropwise adding a silicon source, refluxing to obtain a second solution, centrifugally separating, drying, and calcining to obtain SiO2 nano microspheres; mixing SiO2 nano-microspheres with ethanol, and dispersing the SiO2 nano-microspheres by using ultrasonic waves to obtain a third solution; polyvinylpyrrolidone and a cerium-containing metal salt doping agent are dissolved in ultrapure water and stirred, and a fourth solution containing CeO2 is obtained; mixing the third solution and the fourth solution to form a fifth solution, and dropwise adding an ammonia water solution; and carrying out reflux condensation and aging on the fifth solution, separating the reaction product, and carrying out ultrasonic cleaning, drying and calcining to obtain the CeO2-coated SiO2 composite microspheres. The invention allows for precise control of the size, shape, core, and surface functionalization of the microspheres.

Description

Technical Field

[0001] The invention relates to the technical field of nano-scale microspheres, and in particular to a method for controllably synthesizing cerium dioxide-coated silicon dioxide-based composite microspheres. Background Art

[0002] Cerium dioxide (CeO2) and silicon dioxide (SiO2) based composite materials have a wide range of applications in materials science and engineering. In particular, ceria is widely used in catalysis, abrasives, oxygen sensors and other fields due to its excellent hardness, chemical stability, oxygen reduction performance and low friction coefficient. Silicon dioxide plays an important role in many surface treatments and functional materials due to its good dispersibility and low friction coefficient. However, when ceria and silicon dioxide are used alone, their respective defects limit their effectiveness in some high-end applications.

[0003] In many applications, especially in chemical mechanical polishing (CMP) processes, the choice of abrasives is critical, and silicon dioxide (SiO2) plays an important role in the polishing process due to its uniform spherical particles, narrow particle size distribution, and low cost. However, the soft nature of silicon dioxide leads to a relatively low polishing rate (the polishing rate is in the following order: (CeO2>TiO2>MnO2>Al2O3>SiO2). In order to overcome this shortcoming and improve the polishing efficiency, harder CeO2 particles can be coated on the surface of SiO2 particles, which not only improves the polishing rate, but also reduces the introduction of additional surface defects.

[0004] The synthesis of ceria-coated silica-based composite microspheres has the following advantages: Improved hardness and wear resistance: Ceria has a high hardness. After being coated on the surface of silica microspheres, the overall hardness and wear resistance of the composite microspheres are significantly improved, thereby improving the service life and efficiency of the material; Improved dispersion and uniformity: Silica microspheres have good dispersion, which can prevent the agglomeration of ceria particles and ensure the uniformity of the composite microspheres. This uniform distribution helps to improve the consistency and stability of the material in different applications; Optimized friction performance: Ceria has a low friction coefficient, which helps to reduce wear and improve the stability and performance of the overall material, especially in high-precision processing; Enhanced chemical activity: Ceria itself has a strong oxygen reduction property, which can improve the efficiency of the composite microspheres in the catalytic and surface treatment processes and enhance its wide range of applications.

[0005] However, although ceria-coated silica-based composite microspheres have shown significant advantages in many fields, there are still some problems with existing synthesis methods. For example, the ceria coating is often not uniform enough, resulting in unstable performance of the composite microspheres; at the same time, the reaction conditions in traditional synthesis methods are difficult to control, and the uniformity of particle size and surface structure is often affected. These problems limit the effectiveness and practicality of composite microspheres in certain precision applications. Summary of the invention

[0006] In view of the above-mentioned shortcomings, the present invention proposes a method for controllably synthesizing cerium dioxide-coated silicon dioxide-based composite microspheres, which allows precise control of the size, shape, core, and surface functionalization of the microspheres.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for controllably synthesizing cerium dioxide-coated silicon dioxide-based composite microspheres, comprising the following steps:

[0008] S1: Weigh at least one cationic surfactant and dissolve it in ultrapure water. Stir it at room temperature until it is completely dissolved to form a first solution. Slowly drop a NaOH solution into the first solution and stir vigorously at room temperature for 20 to 40 minutes.

[0009] S2: raising the temperature of the first solution to 70-90° C., slowly dropping a silicon source, and refluxing for 1-2 hours after the dropping to obtain a second solution, centrifuging the second solution, drying to remove residual water, and calcining the dried sample at high temperature to obtain SiO2 nanoparticles;

[0010] S3: mixing the SiO2 nanospheres with ethanol, and dispersing the SiO2 nanospheres by ultrasonic treatment until the SiO2 nanospheres are completely dispersed to obtain a third solution;

[0011] S4: weighing polyvinyl pyrrolidone and at least one cerium metal salt dopant, dissolving them in ultrapure water, and vigorously stirring for 20 to 40 minutes to obtain a fourth solution uniformly containing CeO2;

[0012] S5: the third solution and the fourth solution are mixed and poured into a test container, and vigorously stirred for 20 to 40 minutes at room temperature to form a fifth solution, and the ammonia solution is slowly added dropwise to the fifth solution;

[0013] S6: The fifth solution is subjected to condensation reflux operation at 70-90°C for 2-4 hours. After the reflux, it is aged, and then the reaction products are separated by high-speed centrifugation, and ultrasonically cleaned with a mixed solution of water and ethanol. After repeated ultrasonic cleaning for several times, it is dried in an oven, and the dried sample is calcined at high temperature to enhance its structural stability to obtain CeO2@SiO2 composite microspheres.

[0014] As an improvement, the cationic surfactant in step S1 is one or two of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyldimethylphenylammonium chloride, and di(2-ethylhexyl)sodium sulfosuccinate.

[0015] As an improvement, the concentration of the NaOH solution in step S1 is 5 mol / L, and the amount of the solution added is 0.25 to 0.3 mL.

[0016] As an improvement, the silicon source in step S2 is tetraethyl orthosilicate or sodium silicate.

[0017] As an improvement, the particle size of the SiO2 nanospheres in step S2 is 200-300 nm.

[0018] As an improvement, the ultrasonic dispersion time in step S3 is 10 to 15 minutes.

[0019] As an improvement, the cerium-containing metal salt dopant in step S4 is Ce(NO3)3·6H2O.

[0020] As an improvement, the mass ratio of SiO2 in the third solution in step S3 to CeO2 in the fourth solution in step S4 is in the range of 1:1.5-1:2.

[0021] As an improvement, the pH of the first solution in step S1 and the fifth solution in step S5 is between 9.5 and 10.0.

[0022] As an improvement, the high temperature calcination temperature in steps S2 and S6 is 500-700°C.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) This method allows precise control of the size, shape, core, and surface functionalization of the microspheres. Using specific silicon sources, dopants, and surfactants, we are able to prepare uniform and functionalized composite microspheres suitable for chemical mechanical planarization (CMP) applications.

[0025] (2) Through multiple calcination treatments, the structural stability of the composite microspheres is enhanced, allowing them to maintain excellent performance under high temperature and harsh environments;

[0026] (3) Ultrasonic treatment was used to disperse the SiO2 microspheres, ensuring that CeO2 could be evenly coated on the surface of the SiO2 microspheres, thereby improving the uniformity and dispersibility of the composite microspheres;

[0027] (4) Polyvinyl pyrrolidone (PVP) is a good surfactant and colloidal protective agent. It can help stabilize the dispersion of CeO2 and prevent agglomeration between particles. It can also improve the binding between CeO2 and SiO2, thereby promoting the coating effect. First, polyvinyl pyrrolidone combines with CeO2 to form a protective film on the surface of CeO2 particles, reduce the physical contact between particles, and reduce the risk of aggregation. Therefore, it can improve the dispersion of CeO2 in the solution, ensure that CeO2 is evenly distributed on the surface of SiO2 microspheres, and when CeO2 particles combined with polyvinyl pyrrolidone come into contact with SiO2 particles, polyvinyl pyrrolidone acts as a binder, bonding CeO2 particles to SiO2, improving the interaction force, and achieving the coating effect. According to the particle size, dispersibility and coating uniformity of SiO2, the coating effect of CeO2 on SiO2 microspheres is best when the mass ratio of polyvinyl pyrrolidone to CeO2 is in the range of 1:1.5-1:2. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0029] Figure 1 This is the particle size distribution curve of CeO2@SiO2 composite microspheres in Example 1;

[0030] Figure 2 This is the particle size distribution curve of CeO2@SiO2 composite microspheres in Example 2;

[0031] Figure 3 This is the particle size distribution curve of CeO2@SiO2 composite microspheres in Example 3;

[0032] Figure 4 The scanning electron microscope (SEM) images of SiO2 (a) microspheres and CeO2@SiO2 (b) composite microspheres of Example 1 are shown;

[0033] Figure 5 The scanning electron microscope (SEM) images of SiO2 (c) microspheres and CeO2@SiO2 (d) composite microspheres of Example 2;

[0034] Figure 6 The scanning electron microscope (SEM) images of SiO2(e) microspheres and CeO2@SiO2(f) composite microspheres of Example 3 are shown;

[0035] Figure 7 The transmission electron microscope (TEM) and EDS images of the CeO2@SiO2 (a, b, c) composite microspheres of Example 2 are shown;

[0036] Figure 8Transmission electron microscope (TEM) images and EDS images of CeO2@SiO2 (d, e, f) composite microspheres in Example 3;

[0037] Fig. 9 XRD patterns of SiO2, commercial CeO2, and CeO2@SiO2 composite microspheres in Example 2;

[0038] Fig.10 This is the Fourier transform infrared spectrum (FTIR) of CeO2@SiO2 composite microspheres of Example 2;

[0039] Fig.11 This is the thermogravimetric analysis (TGA) diagram of CeO2@SiO2 composite microspheres in Example 2. DETAILED DESCRIPTION

[0040] Embodiment 1

[0041] S1: Weigh 0.18 g, 0.50 mmol of hexadecyltrimethylammonium bromide (CTAB) and dissolve it in 96 mL of ultrapure water. Stir at room temperature until it is completely dissolved to form a first solution. Transfer it to a 250 mL round-bottom flask, slowly drop 0.25 mL of 5 mol / L NaOH solution into the first solution, and stir vigorously at room temperature for 30 minutes to ensure that the pH of the first solution is 9.5-10.0;

[0042] S2: Raise the temperature of the first solution to 80°C, slowly add 1.34 mL of tetraethyl orthosilicate at a rate of 1 drop / second, reflux for 2 hours after the addition is complete, obtain a second solution, centrifuge the second solution, dry it at 60°C for 12 hours to remove residual moisture, place the dried sample in a constant temperature environment of 500°C for calcination for 2 hours, and obtain SiO2 nanospheres;

[0043] S3: 1.2 g of SiO2 nanospheres were mixed with 50 mL of ethanol, and the SiO2 nanospheres were dispersed by ultrasonic treatment for 10 minutes until the SiO2 nanospheres were completely dispersed to obtain a third solution;

[0044] S4: Weigh 1.0 g of polyvinyl pyrrolidone (PVP) and 1.5 g of Ce(NO3)3·6H2O and dissolve them in 100 mL of ultrapure water, and stir vigorously for 30 minutes to obtain a uniform fourth solution;

[0045] S5: The third solution and the fourth solution are mixed and poured into a 500 mL three-necked flask, and the mixture is vigorously stirred for 30 minutes at room temperature to form a fifth solution, and 20 mL of 20% ammonia solution is slowly added dropwise to the fifth solution to ensure that the pH of the fifth solution is between 9.5 and 10.0;

[0046] S6.1: The fifth solution is subjected to condensation reflux operation at 70° C. for 2 hours. After the reflux, the solution is aged for 8 hours. The reaction product is then separated by centrifugation at 8000 rpm and ultrasonically cleaned using a mixed solution of water and ethanol in a volume ratio of 1:1. The ultrasonic cleaning is repeated three times.

[0047] S6.2: The cleaned composite microspheres were placed in an oven at 60°C for 12 hours for drying, and the dried samples were calcined at 600°C for 2 hours to enhance their structural stability to obtain CeO2@SiO2 composite microspheres.

[0048] Embodiment 2

[0049] S1: Weigh 0.27 g, 0.75 mmol of hexadecyltrimethylammonium bromide (CTAB) and dissolve it in 96 mL of ultrapure water. Stir at room temperature until it is completely dissolved to form a first solution. Transfer it to a 250 mL round-bottom flask, slowly drop 0.3 mL of 5 mol / L NaOH solution into the first solution, and stir vigorously at room temperature for 30 minutes to ensure that the pH of the first solution is 9.5-10.0;

[0050] S2: Raise the temperature of the first solution to 80°C, slowly add 1.34 mL of tetraethyl orthosilicate at a rate of 1 drop / second, reflux for 1.5 hours after the addition is complete, obtain a second solution, centrifuge the second solution, dry it at 60°C for 12 hours to remove residual moisture, place the dried sample in a constant temperature environment of 550°C for calcination for 2 hours, and obtain SiO2 nanospheres;

[0051] S3: 1.3 g SiO2 nanospheres were mixed with 60 mL ethanol, and the SiO2 nanospheres were dispersed by ultrasonic treatment for 15 minutes until the SiO2 nanospheres were completely dispersed to obtain a third solution;

[0052] S4: 1.2 g of polyvinyl pyrrolidone (PVP) and 1.8 g of Ce(NO3)3·6H2O were weighed and dissolved in 100 mL of ultrapure water, and stirred vigorously for 30 minutes to obtain a uniform fourth solution;

[0053] S5: The third solution and the fourth solution are mixed and poured into a 500 mL three-necked flask, and the mixture is vigorously stirred for 30 minutes at room temperature to form a fifth solution, and 20 mL of 20% ammonia solution is slowly added dropwise to the fifth solution to ensure that the pH of the fifth solution is between 9.5 and 10.0;

[0054] S6.1: The fifth solution is subjected to condensation reflux operation at 70° C. for 2 hours. After the reflux, the solution is aged for 8 hours. The reaction product is then separated by centrifugation at 8000 rpm and ultrasonically cleaned using a mixed solution of water and ethanol in a volume ratio of 1:1. The ultrasonic cleaning is repeated three times.

[0055] S6.2: The cleaned composite microspheres were placed in an oven at 60°C for 12 hours for drying, and the dried samples were calcined at 650°C for 2 hours to enhance their structural stability to obtain CeO2@SiO2 composite microspheres.

[0056] Embodiment 3

[0057] S1: Weigh 0.36 g, 1 mmol of hexadecyltrimethylammonium bromide (CTAB) and dissolve it in 96 mL of ultrapure water. Stir at room temperature until it is completely dissolved to form a first solution. Transfer it to a 250 mL round-bottom flask, slowly drop 0.25 mL of 5 mol / L NaOH solution into the first solution, and stir vigorously at room temperature for 30 minutes to ensure that the pH of the first solution is 9.5-10.0;

[0058] S2: Raise the temperature of the first solution to 80°C, slowly add 1.34 mL of tetraethyl orthosilicate at a rate of 1 drop / second, reflux for 2 hours after the addition is complete, obtain a second solution, centrifuge the second solution, dry it at 60°C for 12 hours to remove residual moisture, place the dried sample in a constant temperature environment of 500°C for calcination for 2 hours, and obtain SiO2 nanospheres;

[0059] S3: 1.0 g of SiO2 nanospheres were mixed with 50 mL of ethanol, and the SiO2 nanospheres were dispersed by ultrasonic treatment for 10 minutes until the SiO2 nanospheres were completely dispersed to obtain a third solution;

[0060] S4: 1.0 g of polyvinyl pyrrolidone (PVP) and 2.0 g of Ce(NO3)3·6H2O were weighed and dissolved in 100 mL of ultrapure water, and stirred vigorously for 30 minutes to obtain a uniform fourth solution;

[0061] S5: The third solution and the fourth solution are mixed and poured into a 500 mL three-necked flask, and the mixture is vigorously stirred for 30 minutes at room temperature to form a fifth solution, and 20 mL of 20% ammonia solution is slowly added dropwise to the fifth solution to ensure that the pH of the fifth solution is between 9.5 and 10.0;

[0062] S6.1: The fifth solution was subjected to condensation reflux operation at 70° C. for 3 hours. After the reflux, the solution was aged for 12 hours. The reaction product was separated by centrifugation at 8000 rpm and ultrasonically cleaned using a mixed solution of water and ethanol in a volume ratio of 1:1. The ultrasonic cleaning was repeated three times.

[0063] S6.2: The cleaned composite microspheres were placed in an oven at 60°C for 12 hours for drying, and the dried samples were calcined at 650°C for 2 hours to enhance their structural stability to obtain CeO2@SiO2 composite microspheres.

[0064] Particle size and morphology analysis

[0065] like Figures 1 to 3 As shown, the particle size distribution curves of the CeO2@SiO2 composite microspheres of Example 1, Example 2, and Example 3 reveal the main characteristics of their particle sizes. According to the curve analysis, the main peak position of the particle size distribution of the CeO2@SiO2 composite microspheres of Example 1 is about 500nm, the main peak position of the particle size distribution of the CeO2@SiO2 composite microspheres of Example 2 is about 300nm, and the main peak position of the particle size distribution of the CeO2@SiO2 composite microspheres of Example 3 is about 300nm. The three curves all show a typical normal distribution morphology, among which the particle size distribution curve of the CeO2@SiO2 composite microspheres of Example 2 is relatively concentrated and narrow, which means that the size of most particles is concentrated around 300nm, and the discreteness of the particle size distribution is small, indicating that the particle size distribution of the CeO2@SiO2 composite microspheres of Example 2 is relatively uniform, and the size difference of the particles is small.

[0066] like Figures 4 to 6 As shown in the figure, the scanning electron microscope (SEM) images of SiO2 nanospheres and CeO2@SiO2 composite microspheres show the surface morphology and coating characteristics of both. Figure 4 a, Figure 5 c, Figure 6 In Figure 5, the SiO2 nanospheres in Examples 1 to 3 all exhibited smooth and uniform spherical structures with consistent particle sizes, reflecting good control of the reaction conditions during the synthesis process. Figure 4 In the CeO2@SiO2 composite microspheres in b, some SiO2 nanospheres are coated with a layer of CeO2, but the distribution of CeO2 is uneven, indicating that the coating effect of CeO2 is poor, and there is a phenomenon of incomplete coating or local excess. Figure 5 d shows the SiO2 nanospheres of Example 2, whose surface is uniformly coated with a layer of CeO2, forming a dense and complete composite structure, and the surface features are more complex and uniform, indicating that the CeO2 coating process has been significantly optimized. Figure 6 The SiO2 nanospheres in Example 3 in f are also uniformly coated with CeO2, but the thickness of the coating layer has local differences, that is, some areas are thicker and some areas are thinner, which may be caused by differences in local conditions during the deposition process.

[0067] like Figures 7 and 8 As shown in the figure, the transmission electron microscope (TEM) image and energy dispersive spectrum analysis (EDS) image of CeO2@SiO2 composite microspheres are shown. Figure 7 In a, it can be clearly seen that the CeO2 layer is uniformly coated on the surface of the SiO2 nano-microspheres in Example 2, showing the structural characteristics of the composite microspheres. The thickness of the CeO2 layer is uniform and dense, indicating that the coating process is successful and stable. The element distribution of CeO2 and SiO2 is further verified by the element distribution diagram of the EDS diagram, showing that the CeO2 element is mainly distributed in the outer layer of the SiO2 nano-microspheres, proving the uniformity of the structure and composition distribution of the composite microspheres. This result shows that the CeO2@SiO2 composite microspheres of Example 2 have good structural and composition stability. Figure 8 b shows that, for the CeO2@SiO2 composite microspheres in Example 3, although the CeO2 layer is coated, it fails to form a complete spherical film.

[0068] Surface and chemical composition analysis

[0069] SiO2, commercial CeO2 and CeO2@SiO2 composite microsphere samples of Example 2 were selected for XRD testing. The samples were fully ground and pressed into tablets. The scanning range was set to 10°–80°, the scanning speed was 0.02° / min, and the light source was Cu-Kα ray. XRD analysis results show that Fig. 9 As shown, the pure CeO2 sample (red) presents a typical face-centered cubic (FCC) structure, and its main diffraction peaks are located at 28.5°, 33.1°, 47.5°, 56.4° and 59.2°, corresponding to (111), (200), (220), (311) and (222) crystal planes, respectively, which conforms to the PDF#34-0394 standard card; the SiO2 sample (green) is amorphous, with only a broad peak near 20°, which conforms to the PDF#30-0448 standard; the CeO2@SiO2 composite sample (blue) of Example 2 retains the diffraction peak of CeO2, and the peak position is consistent with that of pure CeO2, but the peak intensity is weakened, indicating that CeO2 still maintains crystallinity under SiO2 coating, and the amorphous characteristics of SiO2 do not change the crystal structure of CeO2.

[0070] The CeO2@SiO2 composite microspheres of Example 2 were tested by Fourier transform infrared spectroscopy (FTIR) in the range of 400–4000 cm -1 . Fig.10 The main characteristic peak is located at about 1100 cm -1 、800cm -1 and 500–600 cm -1 . About 1100cm -1 The peak corresponds to the antisymmetric stretching vibration of Si-O-Si bond, indicating the presence of SiO2; about 800cm -1 The peaks at 500–600 cm are related to the symmetric stretching vibration of the Si-O bond, further confirming the characteristics of SiO2. -1 The peak at 3400cm is attributed to the vibration of Ce-O bond, proving the existence of CeO2. -1 The weak absorption peaks nearby may come from water or hydroxyl groups adsorbed on the surface. Taken together, these characteristic peaks indicate that CeO2 is successfully coated on SiO2 to form a composite structure.

[0071] Thermal performance test

[0072] The thermal stability of the CeO2@SiO2 composite microspheres of Example 2 was analyzed in the range of 25–900°C at a heating rate of 5°C / min. Fig.11 As shown in the figure, the sample mass decreases significantly with increasing temperature. The mass begins to decrease rapidly at about 200°C, indicating that water or volatile substances begin to be lost. As the temperature continues to rise, the mass tends to stabilize and finally drops to about 92% at 800°C, indicating that the CeO2@SiO2 composite material of Example 2 has good high-temperature thermal stability.

[0073] According to the particle size, dispersibility and coating uniformity of SiO2, when the mass ratio of polyvinyl pyrrolidone to CeO2 is in the range of 1:1.5-1:2, the CeO2 in Example 2 has the best coating effect on SiO2 microspheres. The particle size distribution of CeO2@SiO2 composite microspheres is relatively uniform, the size difference of the particles is small, and the thickness of the CeO2 layer is uniform and dense, indicating that the coating process is successful and stable, and has good high-temperature thermal stability.

[0074] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. All changes made within the scope of protection of the independent claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for controllably synthesizing cerium dioxide-coated silicon dioxide-based composite microspheres, characterized in that: The following steps are involved: S1: Weigh at least one cationic surfactant and dissolve it in ultrapure water. Stir it at room temperature until it is completely dissolved to form a first solution. Slowly drop a NaOH solution into the first solution and stir vigorously at room temperature for 20 to 40 minutes. S2: raising the temperature of the first solution to 70-90° C., slowly dropping a silicon source, and refluxing for 1-2 hours after the dropping to obtain a second solution, centrifuging the second solution, drying to remove residual water, and calcining the dried sample at high temperature to obtain SiO2 nanoparticles; S3: mixing the SiO2 nanospheres with ethanol, and dispersing the SiO2 nanospheres by ultrasonic treatment until the SiO2 nanospheres are completely dispersed to obtain a third solution; S4: weighing polyvinyl pyrrolidone and at least one cerium metal salt dopant, dissolving them in ultrapure water, and vigorously stirring for 20 to 40 minutes to obtain a fourth solution uniformly containing CeO2; S5: the third solution and the fourth solution are mixed and poured into a test container, and vigorously stirred for 20 to 40 minutes at room temperature to form a fifth solution, and the ammonia solution is slowly added dropwise to the fifth solution; S6: The fifth solution is subjected to condensation reflux operation at 70-90°C for 2-4 hours. After the reflux, it is aged, and then the reaction products are separated by high-speed centrifugation, and ultrasonically cleaned with a mixed solution of water and ethanol. After repeated ultrasonic cleaning for several times, it is dried in an oven, and the dried sample is calcined at high temperature to enhance its structural stability to obtain CeO2@SiO2 composite microspheres.

2. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The cationic surfactant in step S1 is one or two of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyldimethylphenylammonium chloride, and di(2-ethylhexyl)sodium sulfosuccinate.

3. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The concentration of the NaOH solution in step S1 is 5 mol / L, and the amount of the solution added is 0.25-0.3 mL.

4. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The silicon source in step S2 is tetraethyl orthosilicate or sodium silicate.

5. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The particle size of the SiO2 nanospheres in step S2 is 200-300nm.

6. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The ultrasonic dispersion time in step S3 is 10 to 15 minutes.

7. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The cerium metal salt dopant in step S4 is Ce(NO3)3·6H2O.

8. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The mass ratio of SiO2 in the third solution in step S3 to CeO2 in the fourth solution in step S4 is in the range of 1:1.5-1:

2.

9. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The pH of the first solution in step S1 and the fifth solution in step S5 is between 9.5 and 10.

0.

10. The method for controllably synthesizing ceria-coated silica-based composite microspheres according to claim 1, characterized in that: The high temperature calcination temperature in steps S2 and S6 is 500-700°C.

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